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Topic Review (Newest First)

02-11-2013 10:19 AM

Old Fool

Quote:

Originally Posted by mc73DD189

I should have read this thread before I started mine
Good info! Couple of questions
Does it matter what size blast cabinet you use and if my garage is running on 200 amps, I shouldn't have to change any outlets, correct?

200 amps is the size of the main breaker, the total load the panel will handle.
It has no direct relationship to your outlets.

You need a circuit that is wired with the proper size receptacle, wire and breaker for the load you are going to connect to it .

02-11-2013 10:16 AM

Old Fool

Quote:

Originally Posted by oldred

Fellas you are being concerned about the wrong thing, an 80 gallon tank will make no difference vs a 60 gallon, how could it? Think about it. The tank only stores air the pump puts out it does not nor can not add air, I know what the usual argument is and that's "reserve air" but honestly it don't work that way. Let's take that 60 vs 80 gallon example since that's what usually comes up, if your compressor is running out of air at an annoying rate with a 60 gallon tank just how long would it run if it only had a 20 gallon tank? Mere seconds before cycling on right? Well that's all you would add to the run time but then even that little bit is lost to the proportionally longer recharge time so what was gained? Obviously nothing is gained, all that happens is that with the larger tank you will get a slightly longer run time (usually only seconds under high demand) that is immediately off-set by the proportionally longer recharge time so exactly NOTHING is gained during any given work period, that's NOT the purpose of the larger tank in the first place. No matter how it is cut, sliced or diced over any given work period you will have the same amount of air available regardless of whether the tank is 60 gallons or 80 gallons, the larger tank will have fewer but longer cycles vs the smaller tank's more frequent but shorter cycles but the time spent running vs recharging, all else being equal, is going to be EXACTLY the same! You need to be concerned about the CFM and the compressor's duty cycle and quality because whether you believe it or not a 16 CFM 60 gallon tank compressor would outperform a 15 CFM 80 gallon tank compressor or for that matter the 16 CFM with only a 40 gallon tank would outperform a 14 or 15 CFM unit with an 80 gallon tank! A bigger tank DOES NOT make a bigger compressor!!!

So why are bigger tanks used? A tank is chosen by the designer to balance the run time vs recharge times (duty cycle and cooling) based on CFM and expected demand (on a quality compressor anyway, cheap Chinese units are for another reason) and not to help run time performance. A larger tank can help with wear and power usage over a long period of time due to fewer high load start cycles but over the life of the compressor this is going to be almost negligible between a 60 vs 80 gallon tank with all else being equal. The point is DON'T WORRY ABOUT THE SIZE OF THE TANK! If you choose the right compressor for the job based on the important factors such as CFM, duty cycle and quality then the proper tank size will be chosen by the designer, if it's 60 or 80 gallon then either is just fine and it would be a huge mistake to pass up any of the other factors (especially CFM because if it's low then nothing else matters!) just to get a bigger tank but unfortunately it happens all the time. That's what I meant when I said the cheaper outfits choose a tank for another reason, they are aware that most people simply do not understand the physics behind an air compressor and will go straight to the biggest tank in the store, hey that big tank just looks like a big compressor right? For this reason there are too many compressors out there with woefully under-sized pumps and under-powered motors mounted on uselessly oversized tanks that LOOK big and bad but in operation would be lucky to make enough air to properly blow the hat off your head, that big tank is nothing more than a sales gimmick. When choosing that compressor ask yourself, do I want a compressor that LOOKS impressive or do I want something that will supply the air I need? To get the air you need will mean CFM available at the tool not a big empty tank with a little pump straining to fill it!

Listen to what Old Red is saying as he turns blue in the face repeating himself --- Big tanks mean NOTHING for your usage, they are just a marketing ploy for your misdirection.

Like OR said - in an engineered system the sizing of the tank vs. air consumption vs. run time is considered.

IF you were to commission a study, you would quickly find out you need a compressor about 4 times as large as the maximum anticipated air usage.

That means the air tool that says it uses 12 cfm@90 - you will need an air compressor that makes around 45-50 cfm@90 to be properly sized.

Does this happen, yes in industrial settings.

But it doesn't happen in your garage or mine or most body shops for that matter.

Like OR said, AMPS @ volts and cfm along with the duty cycle are the true measurements of what you are buying.

To step up a bit, large air compressors do not even have storage tanks. The pipe directly into a system that has air receiver tanks located around the facility. The tanks supply a large surge usage supply, but the do NOT increase the output of the compressor(s)

One more time - BIG TANKS MEAN NOTHING to the amount of air the compressor can produce.

Hp X 746 Watts
---------------- = AMPS
Voltage

5 hp x 746w / 220v = 17 amps IF you had 100% efficiency but you wont so multiply the 17 by 1.2 = 20 amps

I would search for a compressor that has a 20+ amp 220 volt motor and not focus to much on the rest of the details.

02-11-2013 09:12 AM

oldred

Quote:

Originally Posted by cruizin uncle bob

As for Harbor freight be careful

HF sandblasters are "iffy" at best and the guns/nozzles are junk that are not worth packing off if they were giving them away! Not only are the nozzles waaaaay too big for anything less than an industrial sized compressor they wear out completely in only a minute or so. Up until recently however HF had about the best buy on a home type compressor that could be found anywhere, I am talking about the U.S. General line that were actually just re-badged American made Belaire brand compressors at only 2/3 the cost of the same outfit with the Belaire name on it. Unfortunately these have disappeared recently to be replaced by a "look alike", it's still painted black but it appears to be a Belaire clone and has been re-branded with the Chicago Pneumatic brand name (or whatever silly name it is). I could be wrong and I hope these are still the Belaire units but I don't think they are, they appear to be copies.

02-11-2013 07:20 AM

cruizin uncle bob

I agree with Red take it from experience get a 220 V 2 stage unit. I have a 7 hp. 2 stage, 80 gallon tank, which I got from Sears, paid $1100.00 4 years ago, found identical unit, just a different color at a Lowe's for about $800.00 a few days later after the fact, so shop around, the unit I have does the job, but under heavy use condensation gets to be a problem, be sure you have water traps and a way to drain frequently. As for Harbor freight be careful, the quality of most tools they sell is just not there, I have a cheap pressure blaster and the valves on it cut out from the abrasive quite fast. I did change the nozzle got a heavy duty one fairly cheap at a head stone dealer, where they blast the marble monuments--kinda weird huh but it gets the job done!

01-27-2013 07:36 PM

oldred

Fellas you are being concerned about the wrong thing, an 80 gallon tank will make no difference vs a 60 gallon, how could it? Think about it. The tank only stores air the pump puts out it does not nor can not add air, I know what the usual argument is and that's "reserve air" but honestly it don't work that way. Let's take that 60 vs 80 gallon example since that's what usually comes up, if your compressor is running out of air at an annoying rate with a 60 gallon tank just how long would it run if it only had a 20 gallon tank? Mere seconds before cycling on right? Well that's all you would add to the run time but then even that little bit is lost to the proportionally longer recharge time so what was gained? Obviously nothing is gained, all that happens is that with the larger tank you will get a slightly longer run time (usually only seconds under high demand) that is immediately off-set by the proportionally longer recharge time so exactly NOTHING is gained during any given work period, that's NOT the purpose of the larger tank in the first place. No matter how it is cut, sliced or diced over any given work period you will have the same amount of air available regardless of whether the tank is 60 gallons or 80 gallons, the larger tank will have fewer but longer cycles vs the smaller tank's more frequent but shorter cycles but the time spent running vs recharging, all else being equal, is going to be EXACTLY the same! You need to be concerned about the CFM and the compressor's duty cycle and quality because whether you believe it or not a 16 CFM 60 gallon tank compressor would outperform a 15 CFM 80 gallon tank compressor or for that matter the 16 CFM with only a 40 gallon tank would outperform a 14 or 15 CFM unit with an 80 gallon tank! A bigger tank DOES NOT make a bigger compressor!!!

So why are bigger tanks used? A tank is chosen by the designer to balance the run time vs recharge times (duty cycle and cooling) based on CFM and expected demand (on a quality compressor anyway, cheap Chinese units are for another reason) and not to help run time performance. A larger tank can help with wear and power usage over a long period of time due to fewer high load start cycles but over the life of the compressor this is going to be almost negligible between a 60 vs 80 gallon tank with all else being equal. The point is DON'T WORRY ABOUT THE SIZE OF THE TANK! If you choose the right compressor for the job based on the important factors such as CFM, duty cycle and quality then the proper tank size will be chosen by the designer, if it's 60 or 80 gallon then either is just fine and it would be a huge mistake to pass up any of the other factors (especially CFM because if it's low then nothing else matters!) just to get a bigger tank but unfortunately it happens all the time. That's what I meant when I said the cheaper outfits choose a tank for another reason, they are aware that most people simply do not understand the physics behind an air compressor and will go straight to the biggest tank in the store, hey that big tank just looks like a big compressor right? For this reason there are too many compressors out there with woefully under-sized pumps and under-powered motors mounted on uselessly oversized tanks that LOOK big and bad but in operation would be lucky to make enough air to properly blow the hat off your head, that big tank is nothing more than a sales gimmick. When choosing that compressor ask yourself, do I want a compressor that LOOKS impressive or do I want something that will supply the air I need? To get the air you need will mean CFM available at the tool not a big empty tank with a little pump straining to fill it!

01-27-2013 06:14 PM

cutthroatkid

Just that fast found a thread that says its bad to add a tank...The 60 is fine for now but for sure want a 80 to plumb my whole shop.

01-27-2013 06:10 PM

cutthroatkid

I don't know what comp your running but I went with the puma 60 gallon https://m.northerntool.com/northernt...?itemId=305175
works great for me.Runs my D/A though it kicks on fairly quick but still I've never had to wait for the comp to catch up.It'll work my blaster,paint guns etc.I do wish I would of got the 80 but Couldn't find a new one in my price range &used comps scare me a bit.I just drain mine often as it builds up a lot of moisture.Takes awhile to fill up from empty but once its full it will keep up.I'm looking online about adding an extra tank.

01-27-2013 05:57 PM

oldred

A compressor for a blast cabinet will need a LOT of CFM and the compressor really should have a 100% duty cycle because it will run a lot. The CFM required will be determined by the size of the blast nozzle and the air pressure regulator setting but even with a relativity low pressure and a small nozzle the air flow requirement will still be high, it's just the nature of the beast. Basically you will be concerned with CFM first (that will be your main concern!) and duty cycle second plus the over-all quality of the outfit, while it's tempting to want the largest tank you can get it's not really all that important and if the other two requirements are there (CFM and Duty Cycle) then the HP and tank will be sized properly by the manufacturer, whatever else you do DON'T pass up higher CFM to get a bigger tank because contrary to popular belief a bigger tank does not make up for lack of CFM!

01-27-2013 05:42 PM

mc73DD189

I should have read this thread before I started mine
Good info! Couple of questions
Does it matter what size blast cabinet you use and if my garage is running on 200 amps, I shouldn't have to change any outlets, correct?

02-21-2010 03:01 AM

cutthroatkid

Great info!

02-20-2010 11:31 PM

hp246

CFM= Cubic feet per minute. SCFM= Standard Cubic Feet per minute (CFM at standardized conditions). I think manufacturers intentionally throw these different terms out to keep the consumer from comparing apples to apples.

Blasting units are probably one of the toughest tools for a compressor. They hog bunches of air. Take a look at the tools that you are considering buying. They should give you an idea of the amount of air they need to operate efficiently. If you buy a compressor for the blasting units, you should be good for most anything else you want to run.

Another thing to keep in mind when you are purchasing your compressor, is the attachments you will need. For a compressor of that size, you are probably going to want to plumb an air line and a drop at least 20' from the compressor. This is especially important if you plan to pant at some point. You will need to put a good filter on the line at the end of the drop. And of course you will want air hose and connections.

Good luck.

02-20-2010 11:03 PM

cutthroatkid

What's the diffrence between cfm and scfm

02-20-2010 09:49 PM

oldred

220 volts is a given since any 110 compressor you are likely to find would be woefully inadequate for a sandblaster. By far the most important consideration is CFM because if it is low (below 15 CFM in this case) then nothing else will make up for it. A two stage compressor is much better than a single of the same HP rating and for a given HP the two stage will produce more CFM, cooler air and run quieter. In most cases HP numbers can be quite exaggerated so look at the AMP rating on the motor data plate to determine the actual motor power, at least 21 AMPs for a five HP motor (a 15 AMP rating is common and is only about 3 1/2 HP regardless of what the manufacturer claims). In any case CFM is what is going to make the difference in whether the compressor is adequate or not so make that the first consideration.

Also contrary to popular belief tank size will have next to nothing to do with how well the compressor will keep up and it absolutely will NOT make up for a lack of CFM! So look for CFM first and resist the urge to be drawn to the biggest tank in the store, you simply will not be able to see any appreciable difference in the way a 60 gallon performs vs an 80 gallon. The larger tank is desirable on a compressor of that size because it will have slightly less wear and power consumption over a long period of time due to fewer high load start-up cycles but run time vs waiting on air recovery time will be the same for a 60 or 80 gallon, the extra 20 gallons will gain only a few seconds of extra run time with a sandblaster and then even that will be lost to the longer recharge time so it is simply a trade off and you will gain exactly nothing. The bottom line is get the larger tank if it don't cost more but don't spend much money to get it and whatever else you do DON'T pass up a compressor with more CFM to get one with a bigger tank! Remember CFM is what runs your tools and a bigger tank does not make a bigger compressor!

02-20-2010 08:04 PM

35prog

My opinion is to buy a compressor that is two stage. I would recommend a 60 or larger, gallon tank, also 5hp would be a minimum. I would also buy on that runs on 220 v as they run much cheaper. It is very tempting to try and save $$ on this piece of equipment. Don't.. it will be regretted. I would look at a farm fleet, or thiesens. Also other things to consider are a cast iron head or aluminum. cfm rating (15 to 17)and psi of 120 to 175 would be ideal. Do you home work and don't settle. You are young and will get a lot of good use out of a good comperssor and alot of greif out of a unit that is not ideal for your needs.

02-20-2010 07:47 PM

cutthroatkid

air compressor&sandblaster question

I'm wanting to buy a sandblaster From harborfreight&I'm not sure how to pick a compressor.I'm also gonna evantually get a bench top blast cabinet.I'm just about to be 17 so I don't have a bunch of money,I'm probally gonna buy a used compressor just need to know what to look for thanx!